Field of the Invention
The invention relates to an optical sensing head, in particular for reading out an optical data memory, and to a method for fabricating such a sensing head.
A conventional optical sensing head, such as is used for example in a CD (compact disk) player or a DVD (digital video disk) player, is generally composed of discrete active and passive components which are produced individually and installed in a hybrid fashion in a metal housing. Such a sensing head typically includes a laser source, optical components such as lenses and beam splitters, a deceleration plate, and detectors for monitor functions and signal functions. In order to measure the tracking, spacing and signal level, the signal detector senses the light that is emitted by the laser diode and reflected by the CD or DVD. The monitor detector is used to check the emitted laser power.
The monitor detector is generally arranged in the vicinity of the laser source. For example it is possible to provide for some of the laser beam to strike a monitor photodiode directly behind a housed laser diode. The signal detector is typically mounted as a single component on the metal housing of the sensing head.
Such a sensing head has a size of approximately 30 mm×40 mm and is relatively large and heavy as a result of the discrete design. The monitor detector and the signal detector are located in separate housings and must be individually adjusted.